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In category theory and its applications to mathematics, a biproduct of a finite collection of objects, in a category with zero objects, is both a product and a coproduct. In a preadditive category the notions of product and coproduct coincide for finite collections of objects. [1] The biproduct is a generalization of finite direct sums of modules.
In mathematics, a relation denotes some kind of relationship between two objects in a set, which may or may not hold. [1] As an example, " is less than " is a relation on the set of natural numbers ; it holds, for instance, between the values 1 and 3 (denoted as 1 < 3 ), and likewise between 3 and 4 (denoted as 3 < 4 ), but not between the ...
An example of a ternary relation in elementary geometry can be given on triples of points, where a triple is in the relation if the three points are collinear. Another geometric example can be obtained by considering triples consisting of two points and a line, where a triple is in the ternary relation if the two points determine (are incident ...
Cartesian coordinates of example points. The main historical example is the Cartesian plane in analytic geometry. In order to represent geometrical shapes in a numerical way, and extract numerical information from shapes' numerical representations, René Descartes assigned to each point in the plane a pair of real numbers, called its coordinates.
In constructive mathematics, "not empty" and "inhabited" are not equivalent: every inhabited set is not empty but the converse is not always guaranteed; that is, in constructive mathematics, a set that is not empty (where by definition, "is empty" means that the statement () is true) might not have an inhabitant (which is an such that ).
The smash product of two circles is a quotient of the torus homeomorphic to the 2-sphere. More generally, the smash product of two spheres S m and S n is homeomorphic to the sphere S m + n . The smash product of a space X with a circle is homeomorphic to the reduced suspension of X : Σ X ≅ X ∧ S 1 . {\displaystyle \Sigma X\cong X\wedge S^{1}.}
The term isomorphism is mainly used for algebraic structures. In this case, mappings are called homomorphisms, and a homomorphism is an isomorphism if and only if it is bijective. In various areas of mathematics, isomorphisms have received specialized names, depending on the type of structure under consideration. For example:
In the mathematics of binary relations, the composition of relations is the forming of a new binary relation R ; S from two given binary relations R and S.In the calculus of relations, the composition of relations is called relative multiplication, [1] and its result is called a relative product.